This invention relates to nozzles for dispensing gasoline into vehicle fuel tanks and more specifically to an interlock system to prevent dispensing of gasoline until the discharge spout of a nozzle is inserted into the vehicle fuel pipe.
Current environmental regulations require in some areas that gasoline vapors displaced from a vehicle fuel tank while being filled are to be recovered in order to prevent their escape into the atmosphere. As part of these requirements, it is foreseeable that an interlock system may be required at some time in the future to prevent the dispensing of gasoline until the vapor receiving system is in contact with the vehicle fuel tank. Even if such a requirement never materializes, it is still desirable to have such an interlock system to encourage the filling station operator to have the vapor receiving system properly in place against the fillpipe before gasoline is dispensed.
The prior art has shown many designs for providing such an interlock system. One common method is to use a mechanical linkage between the face seal of the vapor receiving system and the automatic shut-off system within the nozzle housing itself. This type of a system tends to become overly complicated and significantly adds to the weight of the nozzle as well as to the cost of construction and maintenance.
Another design used a valve located within the discharge spout and connected to the vent line which leads to the automatic shut-off system in the nozzle housing. This valve is then connected to the vapor receiving system in such a manner that it is closed when the vapor receiving system is not in contact with the vehicle fillpipe, thereby preventing the dispensing of gasoline. While this particular design is capable of working, it has at least one drawback in that the linkage mechanism between the valve and the vapor receiving system can greatly limit the flexibility of the vapor receiving system itself, thereby increasing the possibility of not obtaining a tight seal against the vehicle fillpipe.
Another problem sometimes encountered with having a valve located in the vent line is the trapping of gasoline within the vent line by the valve. Under normal operations, when the tank becomes filled, gasoline is drawn into the vent tube due to the suction created by the venturi, which eventually shuts off the nozzle. After the nozzle shuts off but before it is withdrawn from the fillpipe, sufficient time has elapsed so that most of the gasoline has drained out of the vent line and back into the fillpipe. However, when using the valve located in the vent line, withdrawal of the nozzle from the fillpipe may cause some gasoline to become trapped in the vent line. When the nozzle is then placed in an upright position, the gasoline can drain down into the diaphragm chamber inside the nozzle housing. While in many cases this gasoline trapped inside the nozzle may not create any problems, the potential of malfunctioning still exists. Therefore, it is desirable to not alter the vent line operation any more than is necessary.
Preferably, an interlock system should be designed in a way that does not interfere with the movement of the vapor receiving system so that a tight seal is formed reliably each time the nozzle is inserted into the fillpipe. Also, its design should be simple to permit ease of operation as well as to minimize manufacturing costs.
The actuation mechanism of the interlock system should be designed so that it operates automatically during normal use of the nozzle, but permits manual overriding of the system for filling tanks with unusual fillpipe designs. One system for accomplishing this result is shown in the above noted copending application, Ser. No. 635,189, which describes an actuation mechanism activated by the weight of the nozzle itself resting in the end of the fillpipe. It is therefore desirable to use such an actuation mechanism for an interlock system because it operates automatically and permits overriding.
It is therefore desirable to have an interlock system with an interlock and actuation mechanism which meet these considerations with minimal change to the conventional nozzle operation.